Sunan Ghair Muakkadah

Occasionally omitting the sunnah ghair muakkadah before Asr and Esha Salaah

Q: We know it is sunnah to read 4 rakaat salaah before the Asr and Esha Salaah. Will it also be sunnah to purposely leave out these sunnah salaah SOMETIMES, as it is Sunnah Ghair Muakkada. 

Ezample, a person reads the 4 sunnah of Asr on Monday and purposely leaves it out on Tuesday and reads it again on Wednesday. Will this be regarded as a sunnah?